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Thursday, December 31, 2009

This is the wild form of melon Cucumis melo known as Queen Anne's pocket melon. It's about the size of a snooker ball and grows as a weed in melon fields in the US. It's edible but insipid. The main reason for growing it, apart from its ornamental properties, is its incredibly intense melon fragrance. One ripe fruit, which lasts for about ten days before it goes soft, will perfume a whole room. Apparently Victorian ladies used to carry them around in their pockets, as a kind of portable pomander. I've grown it for a few years and found that it looks particularly striking in a hanging basket in the conservatory, where the fruits can dangle down like striped orbiting planets. The plants are quite compact and carry separate male and female flowers, so it pays to deliberately pollinate the female flowers to ensure fruit set. Each plant generally produces about half a dozen fruits. The seeds are hard to come by (I got mine via an exchange with a Dutch botanic garden) but I see from a quick Google search that there are a few suppliers in the US.

Saturday, December 26, 2009

Unusual fruits, strawberries - in more ways than one. In many edible fruits the edible part is formed from the succulent ovary wall that encloses the seed (the fleshy part of a peach, for example) but in strawberries each one of the ‘seeds’ on the outside of the fruit is, in botanical terms, a fruit – a seed inside a tough, dry ovary wall – known as an achene - and the edible part of the fruit is formed from the swollen receptacle that they grow on.

The cultivated strawberry Fragaria x ananassa has a fascinating history. It’s an accidental hybrid between F. chiloensis, which grows along the western seaboard of North and South America as far south as Chile, and F. virginiana which is a woodland species mostly found in eastern North America. Both were eaten by indigenous peoples there before they were brought to Europe in the mid-16th. century, where they were cultivated separately. Their fruits were larger than native European species which made them desirable, but the key event in modern strawberry history was a chance cross-pollination between these two species when they were grown together in France. The offspring was the even larger fruited F. x ananassa, originally known as the pineapple or pine strawberry and first described in 1759. Modern strawberries are descendants of this original cross, probably performed by a bee, but perhaps the most interesting aspect of this accident is that, before it arose, varieties of both parents were known that had a wide range of flavours. As late as 1870, American varieties of the parents were known with flavours that included apple, apricot, cherry, grape, mulberry, raspberry and pineapple. It just so happened that the bee that produced the accidental hybrid must have transferred pollen between strawberry-flavoured parents; had it flown between parents with any of the other flavours, modern strawberries would not be strawberry flavoured – spectators at Wimbledon might have been feasting on raspberry- or cherry-flavoured ‘strawberries’. The flavour of strawberries is biochemically complex and a small change in the constituent compounds is all that’s need for a shift in flavour from strawberry flavour to – say – raspberry flavour. Sadly, almost all those other flavours in the old parental species, which have long disappeared from cultivation, have been lost although I think pineapple-flavoured wild strawberries are still available from a few seed suppliers. You often hear people complain about the insipid taste of modern strawberry varieties grown under intensive cultivation techniques; just imagine how diverse their tastes might have been if all those old parental varieties had been conserved and used in modern breeding programmes. There’s much more fascinating information about the history of strawberries in the Evolution of Crop Plants by N.W. Simmonds, published by Longman in 1976 (ISBN 0 582 44496 9), out of print but obtainable from libraries.

Tuesday, December 22, 2009

If I could only grow one cactus this would probably be the one. It was labelled Notocactus schlosseri when I bought it but now it’s been renamed Parodia erubescens. The specimen in the photo was about 10 years old but it flowers just three years after seed germination and blooms annually thereafter, becoming more showy with every passing year. Older plants like the one above produce a magnificent , tightly packed spiral of flowers that bloom for a couple of weeks, then freely set seed which germinates very quickly. They also produce offsets that can be broken off and rooted, which is useful because old plants become top-heavy once they are about 20 centimetres tall and tend to topple over rather easily.

Saturday, December 19, 2009

The vivid colours and satisfying geometry of florists’ auriculas have fascinated gardeners for almost four and a half centuries and over the last few decades they have undergone something of a revival. The distinctive white centre of the flower is the product of a waxy secretion known botanically as farina (the ‘paste’ in florist’s jargon). The so-called 'alpine' varieties have delicately shaded outer petals that are characterised by rich, clear colours and a velvety texture, while the 'edged' varieties have green petals, with sometimes in rim of farina on their edge. Petals have evolved from leaves and the green-flowered varieties are mutants, where the petals have reverted to their ancestral form. The auricula in the picture is a so-called fancy variety known as Sweet Pastures, which combines several distinctive florist’s auricula characters in a single bloom. Auriculas are reputed to have been brought to England from Europe around 1570 by Flemish weavers or perhaps refugees and became popular plants, with florist's societies soon being established with the aim of breeding varieties to exacting standards of perfection. These are as strict as those defined by dog breeders at Crufts; for example, auricula flowers must always be 'thrum-eyed', with a ring of five stamens in the floral tube aperture, and 'pin-eyed' varieties, where the single stigma occupies the same position, are discarded. By the late 18th. century the best varieties were changing hands at around £20 per plant, an immense amount of money at that time. The plants were bred and shown competitively (as they still are) and some gardens in large country houses even had covered auricula ‘theatres’ where collections flowers could be displayed - see http://www.auriculaandprimula.org.uk/history.html and http://www.nationaltrust.org.uk/main/w-vh/w-visits/w-findaplace/w-calkeabbey.htm A National Auricula Society was founded in 1873, which still thrives as the National Primula and Auricula Society see http://www.auriculaandprimula.org.uk/ and http://www.auriculas.org.uk/

Florists auriculas are probably hybrids between the wild alpine Primula auricula (below) and Primula rubra, possibly with a further cross to another unknown species.

Some year ago I did some research work for a now-defunct company called Neo Plants, which specialised in micropropagation of garden plants - a sterile-culture propagation technique which removes viruses and produces very vigorous, healthy stock. Auricula varieties are traditionally propagated by division and stem cuttings and over time the clonal offspring accumulate viruses which gradually diminish their vigour. Neo Plants got their hands on some old auricula varieties and micropropagated them, producing revitalised and very vigorous plants which flowered profusely. At one time I had a small greenhouse full of these delightful flowers and the fragrance that they produced on a spring morning when they were all in bloom was memorable. I still have a few, and their flowers are something I look forward to all through the winter.

Wednesday, December 16, 2009

The iconic plant of the Uraguayan pampas, whose three metre-tall plumes of seeds are a wonderful sight on a bright autumn day in any garden, although they can be devastated by an October gale. It’s a fairly well-behaved plant in British gardens but in some parts of the world where it has been introduced – including southern Spain – it has self-seeded itself and invaded poor quality agricultural land. Maybe a plant to keep a wary eye on then, when the climate of southern England becomes warmer and drier as this century progresses? It’s a serious pest species in Australia and New Zealand and the Hawaiians are fighting a losing battle against it. You can read more about it at http://www.hear.org/species/cortaderia_selloana/

When I was a kid we had a large pampas grass in the corner of our back garden and we were warned to leave the dangerously sharp-edged leaves alone. They didn’t deter frogs though, that often spent the day sheltering down amongst the leaf bases, where they were safe from predators.

Wednesday, November 4, 2009

This spectacular lily is a native of Africa, where it is the national flower of Zimbabwe, and also of India where it is the state flower of Tamil Nadu. It’s a climber, using its leaf-tip tendrils (see backing photo for the title panel of this blog) to cling to supports. If it’s left to scramble through other plants in a conservatory it will grow to a couple of metres tall and typically produces 5-6 blooms. The plant grows from an underground tuber and is easy to cultivate in a warm conservatory in summer, but you need to be careful to keep the tubers dry during winter, otherwise they rot off very easily. All parts of the plant are poisonous and the tubers particularly so, since they contain the toxic alkaloid colchicine (from which the family name is derived). Like many poisonous plants it has a long history of use in folk medicine and along with several related genera that contain colchicine it has been used to treat gout – see http://www.patient.co.uk/medicine/Colchicine.htm . In Africa and India there has recently been a resurgance in interest in extracting a broad spectrum of medicinally useful and antimicrobial compounds from the plant, even to the extent of growing it as a crop, but it’s those flame-like flowers that make it horticulturally interesting. It's often sold under the names flame lily, Gloriosa superba Rothschildiana or G. rothschildiana, and there are yellow-flowered cultivars available. Older literature places it in the plant family Liliaceae. One distinctive floral peculiarity is the way in which the stigma bends through 90 degrees and pokes out of the side of the flower. This is possibly an adaptation to pollination but there seems to be little information on the pollinators of this plant, other than that bumblebees and purple sunbirds (Nectarinia asiatica) http://en.wikipedia.org/wiki/Purple_Sunbird have been seen visiting it.